TECHNICAL REPORT
Introduction to
Black Powder Contamination
August 2019
“Black PowderTM” (black powder)
contamination is a widely used term
for a highly pervasive particulate
contamination found in all hydrocarbon
facilities and pipelines, water systems,
petrochemical powders, and other fluid
and gas systems. It has many other
names, such as black dirt, sludge, shoe
polish, brown dirt, rouge and black sand,
among others. It typically has a black
or dark gray appearance but can also
Figure 1. Conventional filter system overloaded
with black powder contamination.
be brown or dark red depending on its
specific composition. Black powder can
be dry when found in gas applications,
such as in natural gas systems, or wet
and ‘sludgy’ in hydrocarbon fluid, crude
or amine applications. It primarily
consists of ferrous compounds such as
iron sulfide and iron oxide, as well as
other elements (and related minerals)
such as phosphorous, aluminum,
vanadium, manganese, sodium, calcium,
sulfur, chlorides, silica, carbonates, sand
and many others. Its size can range
Figure 2. Black powder captured on a magnetic
separator system.
significantly, from over 500 microns to sub-1 micron levels. Particle counts
often increase in the sub-50 micron range, and particularly in the sub-10
micron range. All too often, its presence and negative impacts are accepted by
industry as a cost of doing business.
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Formation
The initial formation of black powder
– particularly the iron sulfide (FeS)
component – starts with H2S,
water (H2O) and iron (Fe), as well
as carbon dioxide (CO2). Microbes,
including both sulfate-reducing
and acid-producing bacteria, are
key contributors to the formation of
corrosion-causing sulfur compounds
such as hydrogen sulfide (H2S), both
in the well and in pipeline systems.
The interaction between H2S, even
at very low concentrations, and
carbon steel in the presence of water,
Figure 3. Black powder particulate under microscope.
will cause the formation of FeS compounds. While some FeS formation occurs
downhole in wells, the primary source of the contamination is in pipelines, and
in upstream and midstream facilities where microbes contact iron, such as in
carbon steel in facility and pipeline material. The degradation of this pipeline
material by microbes (as well as erosive influences) can also be evidenced
indirectly by the presence of other elements in black powder contamination
sampling and analysis, such as manganese, copper and silicon.
The conversion of FeS to FeO is an exothermic reaction and a pyrophoric
process, therefore treatment of iron sulfide compounds is required to reduce
the potential combustion hazard (ie. introduction of water or potassium
permanganate). The process of contamination sampling requires that the
sample has limited or no exposure to oxygen in order to preserve the FeS
compounds for proper identification. By not eliminating or minimizing the
exposure of black powder to oxygen, samples may incorrectly identify black
powder as largely consisting of FeO, rather than correctly identifying it as FeS,
which can create safety issues, particularly in the presence of hydrocarbons.
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Effects
Once in a system, black powder will
continue to accumulate through
erosion and abrasion. In relation to
carbon steel, the iron compounds in
black powder are particularly hard.
Black powder particles are prone to
breakage into smaller, highly angular
shapes that result in a very abrasive
contaminant that causes pipeline
Figure 4. Black powder build up in piping.
wear and pitting and the erosion of
coatings and passivating layers. As it is prone to shear into smaller particle sizes,
black powder particle counts in the sub-10 micron size range can be significant.
Management of particles at 10 microns and below can be problematic and
expensive to address with conventional filtration methods.
The effects of black powder on hydrocarbon facilities are well-noted. It has
many negative influences, such as:
• wall loss and excessive wear in pipelines,
• more frequent pigging in pipelines due to accumulation,
• premature wear to compressors, pumps and seals (including bypassing seals
into lubrication systems),
• wear on valves and plugging of meters,
• displacement of storage volumes in tankage,
• reduction of product quality,
• infiltration into heat exchangers and reboilers,
• plugging off conventional filtration systems,
• increase in power/fuel requirements to maintain flows and pressures, and
• upsets to gas treating systems such as amine and glycol and related increases
to power/fuel and chemical costs.
To prevent black powder from accumulating in systems and equipment, and
allowing it to continue downstream, the goal for facility and pipeline operators
should be first to eliminate the conditions for its development through proper
root cause analysis, and secondly to eliminate its presence as early as possible in
the hydrocarbon value chain. Managing black powder requires knowledge and
acceptance of its formation process and presence, and a plan and equipment to
remove it.
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